If an interference wave exists in a received signal, a filter provided in a receiver to cancel such an interference wave can be turned on to cancel the interference wave, whereby the capability of signal reception of the receiver can be improved. On the other hand, if the filter is turned on in case no interference wave exists in the received signal, the reception performance of the receiver will be deteriorated. Therefore, for setting a receiver's capability of reception, it is very important to accurately determine whether an interference wave is included in the received signal in order to determine whether the filter is to be turned on or not.
Here will be explained an example of the interference wave detecting method having so far been adopted in a receiver that receives a signal modulated with the OFDM (Orthogonal Frequency Division Multiplexing) technique.
FIG. 1 is a schematic block diagram of a transmitter 100 and receiver 200.
The transmitter 100 modulates a bit data row for sending with the OFDM technique and sends the modulated data row. As shown, the transmitter 100 includes a data generator 101, IFFT (Inverse Fast Fourier Transform) unit 102, serializer 103, RF processor 104 and antenna 105.
The data generator 101 generates a bit data row to be sent.
The IFFT unit 102 makes IFFT of the bit data row generated by the data generator 101.
The serializer 103 converts the bit data row subjected to IFFT in the IFFT unit 102 into a serial symbol data row in units of a symbol.
The RF processor 104 multiplies the symbol data row converted by the serializer 103 by a carrier to provide an OFDM signal.
The antenna 105 sends the OFDM signal output from the RF processor 104 to the receiver 200 via a transmission channel.
The receiver 200 receives the OFDM signal sent from the transmitter 100 and demodulates the received OFDM signal with the OFDM technique. As shown, the receiver 200 includes an antenna 201, frequency converter 202, interference wave canceling filter 203, deserializer 204, FFT (Fast Fourier Transform) unit 205, error correction unit 206 and interference wave detector 207.
The antenna 201 receives the OFDM signal via the transmission channel.
The frequency converter 202 converts the OFDM signal received by the antenna 201 into an IF (Intermediate Frequency) signal having an intermediate frequency of a carrier of the OFDM signal.
The interference wave canceling filter 203 reduces a frequency component including the interference wave in the IF signal supplied from the frequency converter 202.
The deserializer 204 makes serial-parallel conversion of a symbol data row of the IF signal from which the interference wave component has been canceled by the interference wave canceling filter 203 to provide a bit data row.
The FFT unit 205 makes FFT of the bit data row supplied from the deserializer 204.
The error correction unit 206 makes a predetermined error correction of the bit data row having been subjected to FFT in the FFT unit 205.
The interference wave detector 207 detects whether an interference wave component is included in the bit data row having been subjected to FFT in the FFT unit 205.
In the receiver 200, the interference wave detector 207 to detect an interference wave is provided downstream of the FFT unit 205 that makes FFT of a received signal and the interference wave canceling filter 203 provided upstream of the FFT unit 205 is turned on the basis of the result of detection from the interference wave detector 207.